Manage your subscription

Corals living on edge could escape climate change

By Wendy Zukerman

The fringes of communities are hotbeds of creativity – even for corals. A new study shows that Caribbean corals living on the outskirts of a reef evolve novel traits much faster than those at its heart. The findings suggest that conservation efforts for endangered corals might be missing a trick.

The study is one of the few to consider the rate of evolution as a factor for conservation, rather than simply the number of species in an ecosystem. “Evolution is the key to survival for life on Earth,” says Pandolofi, so it makes sense to assess an ecosystem by its evolutionary potential rather than just the number of species it holds.

“It’s fantastic,” says Chris Fulton, an evolutionary marine biologist at the Australian National University, Canberra, who was not involved in the study. “Rather than being marginal players battling to survive, the study shows that corals living on the fringe are powerhouses of diversity.”

John Pandolfi at the University of Queensland, Australia and Ann Budd at the University of Iowa, US, analysed the physical and genetic changes in the Montastraea annularis, a species of coral that has lived in the Caribbean for over 6 million years. They took samples from hundreds of fossilised, extinct and live corals.

Advertisement

Morpho-species

“Evolutionary changes occurred much more often across the edges of the species ranges,” says Pandolfi. Over millions of years, several distinct adaptations were observed in coral surrounding Barbados and the Bahamas, which sit on the margins of the Caribbean reef system. In contrast, samples taken from central locations were static.

Corals need specific conditions to survive. In locations where the water becomes too hot, too acidic, or too deep, they can’t grow out further and push the boundaries of their settlement. Coral on these margins are living in the most extreme environmental conditions that the species can survive, says Pandolfi.

He says this harsh environment has pushed coral to evolve faster into slightly different “morpho-species”. “Where there is a lot of environmental flux you get strange evolutionary changes occurring,” he adds.

And it may apply to other groups of species too&colon; Fulton believes the results could easily be applied to terrestrial animals living in marginal communities.

Pandolfi and Budd’s findings could influence how conservationists choose areas to protect. Traditionally, they have focussed efforts on regions populated with a great number of different species, or large numbers of highly unique species. “We aren’t poo-pooing that idea,” says Pandolfi.

Eco-margins

But it does not take into account how fast communities are evolving. Their study suggests conservation efforts should take a close look at the margins of ecosystems – a point which Fulton embraces, given the threat of climate change.

Since the fringe-dwellers are accustomed to evolving rapidly, Fulton says they may produce changes in a species that help it adapt to climate change – or even produce a new species entirely.

Malcolm McCulloch, an oceanographer at the University of Western Australia, isn’t so sure. The study’s Caribbean corals have evolved as the environment around them changed slowly over the past 6 million years – the very rapid environmental changes happening now may be too much even for the creative fringes of coral reefs, he says.

But he agrees with the implications for conservation. The limited resources of most conservation efforts are put towards protecting central reefs, “because they were thought to have the best chances of survival”. This finding questions that logic, he says.